Six hundred yards. Five hundred. Four-fifty. Four hundred. I crashed the telegraph handles over to "Full speed ahead!" on both engines, and never moving my eyes for an instant from the periscope, directed the helmsman to steer straight for it. The submarine was lying motionless and inert there, some fifteen feet beneath the surface; and I calculated that it would take the Russians at least half a minute to realise that they were discovered, and to get way upon their craft; and by that time we should be so close to them that it would be impossible for them either to dive or to turn the submarine bows on to us, much less to escape. Then, as I felt the destroyer leap forward beneath me, like a spirited horse at the cut of a whip, I blew my whistle, as a signal to "Sparks," who instantly wirelessed back to the main body to stop until further orders, and to keep a sharp lookout for submarines. Like a greyhound slipped from the leash, the _Kasanumi_ rushed at that luckless periscope, about which a few bubbles of foam were just beginning to gather at the moment when our stem, towering over it, hid it from my sight. The next instant our hull swept over it and of course snapped it clean off, although we felt no shock whatever, for our draught of water was too light for our keel to reach the submarine's conning tower. But by the loss of her periscope the craft was effectually blinded, and now she was at our mercy, for she _must_ come to the surface, sooner or later, while, so smooth was the water, the swirl or wake of her as she forged ahead was clearly perceptible, and all we now had to do was to follow her until she rose, and then take or sink her. As I lost sight of the periscope, I rang down to stop and reverse both engines, at the same time ordering our helm hard a-port. Then, as we checked and lost way, we went ahead, first on our port engine and then on both, at the same time shifting our helm, so as to get into the wake of the submarine. We managed to do this before quite losing sight of the disturbance made by her passage through the water; and, this done, we regulated our pace by hers, maintaining a distance of about fifty fathoms between her and ourselves. She shifted her helm several times in an evident attempt to baffle pursuit; but, thanks to the tell-tale swirl she raised, we were able to follow her; and at length, after a chase of about three-quarters of an hour, she rose to the surface, the watertight door of her tower opened, and a man's head appeared.